Jim Carrey stoops to new highs in low comedy: Actually he bends over, flaps his cheeks and introduces the world to butt ventriloquism in "Ace Ventura: Pet Detective." A riot from start to finish, Carrey's first feature comedy is as cheerfully bawdy as it is idiotically inventive.

Carrey's physical clowning and mad brand of humor will be familiar to fans of TV's "In Living Color," for which he created such uniquely insane characters as the pyromaniacal Fire Marshal Bill and the steroid-stuffed bodybuilder Vera de Milo. While Ace Ventura has some attributes in common with Bill and Vera, he is much more endearing than either of those two pucksters. For one thing, he really, really cares about animals.

Ace's apartment resembles a petting zoo, with a skunk in the hamper, an otter in the toilet bowl and two penguins in the refrigerator in addition to squirrels, lizards, raccoons and a variety of more commonplace domestic animals. "I don't do people," explains Ace, who is hired to solve the kidnapping of the Miami Dolphins' mascot, Snowflake, which is followed by the disappearance of quarterback Dan Marino (looking embarrassed and uncomfortable). Ace agrees to locate Snowflake, but he leaves the finding of Marino to his nemesis, the mean-spirited and mysterious police Lt. Einhorn (Sean "What Career?" Young).

During his unorthodox investigations, he wins the heart of the Dolphins' demure marketing director (Courteney Cox), who sees the inner beauty beneath Ace's Value Village wardrobe, his Bob's Big Boy hair, beaverish overbite and completely inappropriate behavior. Watching him commune with her own pup, she is touched by his empathy. "You really love animals, don't you?" she asks. "If it gets cold enough," he retorts.

The ripostes and concept originated with writer Jack Bernstein, then were honed and supplemented by first-time director Tom Shadyac and kooked up by Carrey -- all three of whom are credited for the skeletal screenplay. A spoof of detective movies, the story touches all the bases. Ace has a good buddy -- the one who ends up talking to his butt. He is the precinct cop who reluctantly leaks him information. Then there's the aforementioned game dame, Lt. Einhorn, who has a secret stake in the whereabouts of Snowflake.

They act as foils for Carrey, who probably could have worked solo and still made the movie work, considering he's got more energy to expend than the Tennessee Valley Authority. As with the most memorable clowns, he's got enormous athleticism and flexibility. At one point he pulls himself into a cardboard box to elude the caretakers of an insane asylum. For this scene he is in a pink tutu and boxer shorts. Sometimes it's just Jim in his birthday suit.

Carrey will do anything for a laugh, up to and including stuffing a bathroom plunger into his mobile mouth. Basically, you have to see it to believe it. And if you love bawdy, gut-busting hilarity and stupid pet tricks then this is your "Ace."